The cause now of behaving foolishly is a mischievous ignorance; I mean by this expression, not an ignorance of such things
 
as are matters of instruction but an alienation from, and dislike of knowledge.
The cause again of insensibility is a treacherous and mutilated ignorance. The cause of insatiability is a most grievous appetite for the indulgence of the passions of the soul. The cause of cheerfulness is at once the acquisition and the employment of virtue. Of nakedness there are many causes—an ignorance of such things as are opposite to one another; complete innocence and simplicity of manners; truth, which strips off all the coverings of such things as are concealed, on the one side revealing virtue to our eyes, and on the other side, in its turn, uncovering vice; for no one can possibly put off both these things at one time, nor can he either strip them both off together. But when any one discards the one, he must of necessity take up and clothe himself with the other. For as the old story tells us, God, when he had combined pleasure and pain, two things naturally at variance, under one head, gave to us an outward sense capable of appreciating them both, not at the same moment, but at different times, fixing the period of the return of one to be simultaneous with the moment of the flight of the other. Thus from one root of the dominant principle, the two shoots of virtue and vice sprang up, neither blossoming nor bearing fruit at the same time; for when the one loses its leaves and fades away, then the other begins to shoot, and blossom, and look green, so that one might fancy that the one withered through dissatisfaction at the blooming appearance of the other.
It is with reference to this that Moses represents in a most natural manner the departure of Jacob to be contemporaneous with the arrival of Esau; "For it came to pass," says he, "that as Jacob went out his brother Esau came in." Genesis xxvii. 30. As long, indeed, as prudence dwells in and makes his abode in the soul, so long every companion of folly is discarded and banished to a distance; but when prudence departs then folly rejoices and enters, since its enemy and adversary, for whose sake it was driven away and banished, is no longer inhabiting the same place as before.